This invention relates generally to the filtering art, and more specifically to biological treating systems for aerobically treating wastewater.
Biological treating systems, particularly for the secondary treatment of domestic and/or industrial wastewater, are commonly employed in wastewater treatment installations. These systems include surfaces upon which aerobic biological slimes are grown, and these slimes assimilate, as a food source, the pollutants in the wastewater.
One of the better known biological systems for aerobically treating wastewater employes moving biological contactors in the form of rotating discs, and is manufactured by Autotrol Corporation of Milwaukee, Wis. Autotrol holds numerous patents relating to rotating biological contactors and to various different types of wastewater treatment facilities in which such contactors may allegedly be utilized. U.S. Pat. Nos. 3,827,559 (Gass et al); 3,894,953 (Torpey) and 3,932,273 (Torpey et al) are but a few of the patents owned by Autotrol that relate to the use of rotating biological contactors for aerobically treating wastewater.
In the Autotrol systems the aerobic treatment of wastewater is carried out by connecting the contactors to centrally disposed rotatable axles, and rotating the axles with the contactors in a partially submerged condition within the wastewater. In this manner the biological slimes are exposed to oxygen on the portions of the rotating contactors that are not submerged in the wastewater, and these slimes will then feed upon the pollutants in the wastewater when they are submerged therein. The range of shapes and sizes of rotating contactors that can be satisfactorily utilized in the aerobic treatment of wastewater is limited by the fact that such contactors have to be designed so that they are capable of continually rotating in a partially submerged condition within the wastewater while being rotatably supported on a centrally disposed axle; preferably with the axle positioned above the wastewater.
A different type of system employing moving filter elements is disclosed in U.S. Pat. No. 4,026,802, issued to Akae. In this system modular filters of the type that can provide biological treatment to wastewater are connected together in a closed loop, and are continuously rotated in a single direction through the wastewater to be treated. In forming this closed loop arrangement it is necessary to mount components, such as guide rolls, directly within the filter tank beneath the upper surface of the wastewater. If these submerged components malfunction it is necessary to completely stop the operation of the system and drain the chamber to effect repair. Moreover, since all of the modules are connected together in a continuous, closed loop, it is necessary to stop the rotational motion of the entire loop in the event that repair or replacement of either the chain drive or a particular module is necessary. Both of these latter conditions can result in undesirable downtime in the treatment operation.